Human government is like that crazy uncle who hides a quarter in his fist behind his back, then asks you to guess which fist the quarter is in...No matter which side you choose, Left or Right, both Sides are empty.

You'll have to take the log-in issue to a Linux forum. Did you try the search I recommended? I did. There were lots of results.

Think of it this way: Virtualbox is a "hardware" provider. If you installed an OS on a PC with a Gigabyte motherboard, and the OS stopped being able to log in, you would probably not ask Gigabyte about how to fix it.

If the Virtualbox window is running something related to the guest OS, such as showing an error message from the guest OS, and you are not getting any Virtualbox popups claiming issues with Virtualbox, then chances are really good that Virtualbox is working and the problem is within the guest OS.

One thing you can do is install another Linux guest, then attach the non-log-in-able guest's virtual drive to the new guest. Use the new guest to get files off the old guest's virtual drive.

Human government is like that crazy uncle who hides a quarter in his fist behind his back, then asks you to guess which fist the quarter is in...No matter which side you choose, Left or Right, both Sides are empty.

After receiving black screen, used ctl-alt-F2 to get a login prompt.Logged in as root, found a large file to remove.Terminated VBox, and was able to successfully restart VBox without the GNOME Power Manager error.